Composite decking does have some drawbacks, however, which make it more suitable for some applications than others. These are:
1. Real wood really does look spectacular. Composites can have some rather fake-looking grain.
2. Composite decking is heavier and much less rigid than redwood in general, which means much more under-structure is required. Code for redwood is 30” spacing of joists and beams (though many contractors use 24” to reduce bounce), whereas code for Composite decking is 16”. This often makes it uneconomical to retrofit Composite decking to an existing deck, because you have to put an additional joists in between every existing one, and the joists are probably in bad shape if the deck boards need replacing.
3. Water markings, action of lichen and differential sun shading effects on a composite deck surface can be hard to eliminate and not painting or staining the deck is one of the reasons you went for composites in the first place! Cheap composites are very prone to nonremovable lichen stains which can look awful after a few years.
4. It is rare to find handrails in composite products, probably because composite does not yet have the strength required. This may mean you have to use redwood for the handrails. In which case you might want to consider cable rail systems on new decks.
5. Environmentally, of course, redwood trees produce oxygen for the atmosphere, and employment in forested areas.